Heating continuously traveling metal strip



April 8, 1950 F. MIESS HEATING CONTINUOUSLY TRAVELING METAL STRIP FiledApril 2, 1948 7//// #7 QW A jizwwwza I w /M III,

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Patented Apr. 18, 1950 HEATING CONTINUOUSLY TRAVELING METAL STRIP FredMiess, Gary, Ind.

Application April 2, 1948, Serial No. 18,544

5 Claims.

This application relates to metal heating broadly but is particularlyconcerned with continuously heating metal strip and is acontinuation-in-part of my copending application, Serial No. 528,747,filed March 30, 1944, now Patent No. 2,441,500. One usual way of heatingmetal strip is to cause the strip to longitudinally travel continuouslythrough a continuous furnace provided with metal heat radiators in theform of either metal tubes inside of which a combustible mixture burnsor electric resistance elements. At the present time the metallurgicalart cannot provide commercially usable metal, for making these heatradiators, which can safely operate above about 2000 F., so it isimpossible to heat the metal to higher temperatures although this wouldbe desirable in some instances. Although higher temperatures might beobtained by burning flames directly inside the furnace in contact withthe metal being heated, this is undesirable because it damages the metalbeing heated. Since presently available furnace refractory materials canbe operated safely up to temperatures of 2400" F. and higher, thetemperature limiting factor is set by the metal from which the heatradiators must be made.

With the above in mind, the object of the present invention is toprovide for heating metal, particularly continuously traveling metalstrip to higher temperatures than the metal heat radiators now availablecan be operated, namely, to temperatures above 2000 F. and, in fact, totemperatures limited only by available furnace refractory materials.

Another object is to provide for the heating of reference numeral 2indicates a heating compartment having metal heat radiators 4 thereingenerally constructed according to prior art principles. fed from a coil6 by pinch rolls 8 between the heat radiators 4 and then through guiderolls l0 into a second heating compartment l2. In this compartment arelatively thin wall of thermal insulation l4 surrounds the strip S.Heat is sup- The strip S to be heated is continuously iii) plied to thestrip by means of a high frequency inductor it which surrounds the wallIt and the strip S. In some instances it is deemed desirable to providea relatively thick wall of thermal insulation I8 around the inductor Hi.If the wall I8 is omitted, the high frequency inductor coil l6. whichmay be air or water cooled, will have a temperature not much above roomtemperature. When the wall 18 is included, the coil IE will have atemperature intermediate that of the strip S and the surroundingatmosphere. Under these circumstances the FR loss in the coil would begreater, but this loss would be more than off-set by the reduction ofheat loss from the furnace. With this construction it is possible tohave the coil i6 close to the strip so that good efiiciency is obtained.From the compartment I2 the strip S passes to an open flame compartment20. In this compartment a wall of thermal insulation 22 is providedbetween the strip S and the combustion chamber 24. As the strip S leavesthe compartment 20, it passes between pinch rolls 26 to a coiler 28. Itwill be understood that cooling means such as shown in my aboveidentified copending application could be inserted between the pinchrolls 26 and coiler 28.

A curve of typical strip temperatures at various parts of the furnace isshown in Figure 2. As the strip enters compartment 2 it will have atemperature of approximately which will be increased to approximately1900 by direct radiation in this compartment. In compartment [2 thestrip is heated to a temperature of 2300 by means of the high frequencyinduction coil It. In compartment 20 no heat is supplied to the strip S,but the temperature will be maintained at 2300 F. This is the soakingzone and heat loss from the strip is prevented by means of the heat inthe chamber 24 which is maintained at 2300 F. Since the strip is also at2300" F., it will be clear that there will be no heat flow through thewall 22. If desired, deoxidizing atmosphere can be delivered tocompartments 2, I2 and 20 around the strip S.

While one embodiment of my invention has been shown and described, itwill be apparent that other adaptations and. modifications may be madewithout departing from the scope of the following claims.

I claim:

1. A continuous metal strip heating furnace including the combination ofheat radiators positioned along its length adjacent its entrance end,said radiators being exposed to the strip, open flame compartmentspositioned along the length 3 of the furnace adjacent its exit end, apartition between said compartments and the strip traveling path, and ahigh frequency inductor positioned along the length of the furnacebetween said metal heat radiators and said open flame compartments.

2. A continuous metal strip heating furnace including the combination ofheat radiators positioned along its length adjacentits entrance end,

said radiators being exposed to the strip, open flame compartmentspositioned along the length of the furnace adjacent its exit end, apartition between said compartments and the strip traveling path, a highfrequency inductor positioned along the length of the furnace betweensaid metal heat radiators and said open flame compartments, and a wallof thermalinsulation between said inductor and the strip traveling path.

3. A continuous metal strip heating furnace including the combination ofheat radiators positioned along its length adjacent its entranceend,said radiators being exposed to the strip, open flame compartmentspositioned along the length of the furnace adjacent its exit end, apartition between said compartments and the strip traveling path, a highfrequency inductor positioned along the length of the furnace betweensaid metal heat radiators and said open flame compartments, a relativelythin wall of thermal insulation between said inductor and the striptraveling path, and a relatively thick wall of thermal insulationsurrounding said inductor.

4. A method of heating a, continuously moving metal strip in a furnacehaving heat radiators with a limited safe operating temperature maximum,said method comprising heating said radiators to temperatures close tobut below their safe operating temperature maximum, passing said stripthrough said furnace to directly expose said radiators theretosumciently to heat the strip to a temperature close to but below saidmaximum temperature, then passing the strip through a high frequgncyinductor to raise its temperature to a temperature higher than saidmaximum while shielding and thermally insulating said inductor from saidstrip, and then passing said strip through open flame compartmentsoperating at said higher temperature while isolating saidstrip from saidopen flames.

5. A method of heating a metal charge in a furnace having a plurality ofheat radiating means with a limited safe operating temperature maximum,said method comprising heating said means to temperatures close to butbelow said maximum, directly exposing said means to said charge tothereby heat said charge to a temperature close to but below'saidmaximum by direct radiation, then passing the charge through a highfrequency inductor to raise its temperature to a temperature higher thansaid maximum while shielding and thermally insulating said inductor fromsaid strip, and then passing said charge through open flame compartmentsoperating at said higher temperature while isolating said charge fromsaid open flames.

FRED MIESS.

' file of this patent:

UNITED STATES PATENTS Number Name Date 1,624,668 Kochendorfer Apr. 12,1927 1,646,498 Seede Oct. 25, 1927 1,676,685 Cammen July 10, 19281,799,102 Kelley Mar. 31, 1931 1,890,065 Meehan Dec. 6, 1932 2,130,756Malam Sept. 20, 1938 2,218,354 Keller Oct. 15, 1940 2,420,377 Jones May13, 1947

